drilltools
What is the drill bit on the far left hand side of the machine in the first picture?
I believe it cuts holes shaped liked those in the second picture, which is something I'm trying to achieve. Is it a large countersink bit? I think the hole is about 24mm wide.
Buy a self centering dowel drilling jig. Lee Valley has them, as will virtually all wood working supply sources, Rockler, for example.
The jig clamps to the end of your board, and then you drill through a hardened drill guide into the board, using a hand drill. These dowel jigs used to be much more common in the days before biscuits, pocket screws, etc.
If you are wary of making the holes larger (which is possible and as Tester101 says just make the hole in the tile larger) then you could just go for a smaller anchor and screw.
Obviously this will depend on whether the smaller screws are still a good fit for the holes in the hook. Also the load the hook can take might be reduced, but as you're not going to be swinging from it (hopefully!) you should be OK.
Best Answer
That is a countersink. I would not call it a drill bit, as it's intended to open and shape a hole. Typically a through-hole of the smallest diameter is drilled, then the countersink is performed as a secondary operation. It is typically not advisable to try and "drill" a hole with a countersink.